German published patent No. 36 05 191 describes anti-tumor acting (1-benzylethylenediamine)-platinum(II) complexes of the general formula: ##STR2## in which the radicals R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and represent hydrogen, a C.sub.1 -C.sub.6 -alkyl group, a benzyl group or a phenylethyl group, and B is a thienyl radical, an indolyl radical, an imidazolyl radical or a phenyl radical substituted by the radicals R.sub.5, R.sub.6 and R.sub.7 and the radicals R.sub.5, R.sub.6 and R.sub.7 are the same or different and represent hydrogen, halogen, trihalogen methyl, C.sub.1 -C.sub.6 -alkyl, hydroxy, C.sub.1 -C.sub.6 -alkoxy, phenoxy, benzyloxy, C.sub.1 -C.sub.6 -alkanesulfonyloxy, carboxy, carbalkoxy, cyano, aminocarbonyl, aminocarbonyl containing one or two C.sub.1 -C.sub.6 -alkyl radicals, C.sub.1 -C.sub.6 -alkylcarbonyl, nitro, amino, C.sub.1 -C.sub.6 -alkamino, di-C.sub.1 -C.sub.6 -alkylamino, (C.sub.1 -C.sub.6 -alkyl).sub.3 N.sup.+, C.sub.1 -C.sub.6 -alkanoyl-amino, C.sub.1 -C.sub.6 -alkyl-C.sub.1 -C.sub.6 -alkanoyl-amino, C.sub.1 -C.sub.6 -alkanesulfonylamino, C.sub.1 -C.sub.6 -alkyl-C.sub.1 -C.sub.6 -alkanoylamino, aminosulfonyl, aminosulfonyl containing one or two C.sub.1 -C.sub.6 -alkyl radicals, C.sub.1 -C.sub.6 -alkoxysulfonyl (--SO.sub.2 --O--C.sub.1 -C.sub.6 -alkyl), sulfo(--SO.sub.3 H) or C.sub.1 -C.sub.6 -alkanesulfonyl and two of these radicals can also be the methylenedioxy group and X stands for the equivalent of a physiologically acceptable anion.